Despina (moon)
From Wikipedia, the free encyclopedia
 Despina as seen by Voyager 2 (smeared horizontally) |
|
| Discovery | |
|---|---|
| Discovered by | Stephen P. Synnott[1] and Voyager Imaging Team |
| Discovered in | July 1989 |
| Orbital characteristics[2] | |
|
|
|
| Semi-major axis | 52 526 ± 1 km |
| Eccentricity | 0.0002 ± 0.0002 |
| Orbital period | 0.33465551 ± 0.00000001 d |
| Inclination | 0.216 ± 0.014° (to Neptune equator) 0.06° (to local Laplace plane) |
| Is a satellite of | Neptune |
| Physical characteristics | |
| Dimensions | 180×150×130 km[3] |
| Mass | ~2.1×1018 kg (based on assumed density) |
| Mean density | ~1.2 g/cm3 (estimate) |
| Rotation period | assumed synchronous |
| Axial tilt | ~zero presumably |
| Albedo (geometric) | 0.09[3] |
| Surface temp. | ~51 K mean (estimate) |
| Atmosphere | none |
Despina (des-pee'-nə or sometimes des-pye'-nə, IPA: [dɛsˈpiːnə], IPA: [dɛsˈpaɪnə], Latin Despœna from Greek Δέσποινα), or Neptune V, is the third closest inner satellite of Neptune. It is named after Despina, a nymph who was a daughter of Poseidon.
Despina was discovered in late July, 1989 from the images taken by the Voyager 2 probe. It was given the temporary designation S/1989 N 3.[4] The discovery was announced (IAUC 4824) on August 2, 1989, but the text only talks of "10 frames taken over 5 days", giving a discovery date of sometime before July 28.
Despina is irregularly shaped and shows no sign of any geological modification. It is likely that it is a rubble pile re-accreted from fragments of Neptune's original satellites, which were smashed up by perturbations from Triton soon after that moon's capture into a very eccentric initial orbit.[5]
Despina's orbit lies close to but outside of the orbit of Thalassa and just inside the Le Verrier ring. As it is also below Neptune's synchronous orbit radius, it is slowly spiralling inward due to tidal decceleration and may eventually impact Neptune's atmosphere, or break up into a planetary ring upon passing its Roche limit due to tidal stretching.
[edit] References
- ^ Planet Neptune Data http://www.princeton.edu/~willman/planetary_systems/Sol/Neptune/
- ^ R.A. Jacobson and W.M. Owen Jr. (2004). "The orbits of the inner Neptunian satellites from Voyager, Earthbased, and Hubble Space Telescope observations". Astronomical Journal 128: 1412.
- ^ a b E. Karkoschka (2003). "Sizes, shapes, and albedos of the inner satellites of Neptune". Icarus 162: 400.
- ^ IAUC 4824 discovery IAUC circular
- ^ D. Banfield and N. Murray (1992). "A dynamical history of the inner neptunian satellites". Icarus 99: 390.
| Moons of Neptune | |
|---|---|
| Naiad · Thalassa · Despina · Galatea · Larissa · Proteus · Triton · Nereid · Halimede · Sao · Laomedeia · Psamathe · Neso | |
